1. Field of the Disclosure
The disclosure relates to a rotor disc for a vacuum pump, in particular a turbomolecular pump, as well as to a rotor comprising such rotor discs.
2. Discussion of the Background Art
Vacuum pumps, such as in particular turbomolecular vacuum pumps, have a rotor shaft supported in a pump housing. The rotor shaft which is driven in particular by an electric motor carries a rotor surrounded by a stator arranged in the pump housing. In particular turbomolecular pumps comprise a plurality of rotor discs. The individual rotor discs comprise a plurality of rotor blades. Stator discs of the stator surrounding the rotor are respectively arranged between adjacent rotor discs, the stator discs also having stator blades.
It is known to produce the rotor of a turbomolecular pump as a single piece. In this regard, the individual rotor discs are manufactured from a solid block, in particular by milling. This is an extremely tedious and expensive method. With such rotors, the stator discs are most often of a two-part design so that they can be inserted between two adjacent rotor discs from outside.
It is further known from DE 10 2007 048 703 to assemble a rotor for a turbomolecular pump from individual rotor discs. In this case, the individual rotor discs are connected with each other via reinforcement rings, each disc having in particular a plane of rotor vanes. The reinforcement rings respectively surround an inner ring of the rotor disc. A rotor of a vacuum pump built from a plurality of rotor discs is manufactured using mechanical joining methods. For this purpose, the inner ring of the rotor disc is oversized with respect to the reinforcement ring. Joining is performed by heating or cooling the components to be joined and by subsequent pressing. This is disadvantageous in that the joining process introduces tensions into the inner ring or the hub of the rotor disc. Further tensions occur due to the great centrifugal forces, as well as to the different thermal expansions of the rotor disc and the reinforcement ring during operation.
It is an object of the present disclosure to provide a rotor disc and a rotor having a plurality of rotors discs, wherein the occurrence of tensions is reduced, in particular at the inner ring of the rotor disc.